Carburetor throttle control



July 5, 1966 H. c. BAER CARBURETOR THROTTLE CONTROL 2 Sheets-Sheet 1Criginal Filed June 27, 1961 HOWARD C. 5145/? INVENTOR. BY %5 ATTORNEYSJuly 5, 1966 H. c. BAER CARBURETOR THROTTLE CONTROL Original Filed June27, 1961 3 Sheets-Sheet 2 HOWARD C. BAER INVENTOR.

KWM w d/W A TTORNEYS United States Patent M 3,259,376 CARBURETORTHROTTLE CONTROL Howard C. Baer, Detroit, Mich, assignor to Ford MotorCompany, Dearbom, Mich, a corporation of Delaware Continuation ofapplication Ser. No. 119,934, June 27,

1961. This application Apr. 12, 1965, Ser. No. 449,375

2 Claims. (Cl. 261-23) This application is a continuation of mycopending application S.N. 119,934, filed June 27, 1961, now abandoned.

This invention relates to multistage carburetors and more particularlyto a mechanism for controlling the operation of the secondary throttlevalve of two stage carburetors.

In recent years, two stage carburetors have been widely used forautomotive engines, particularly those having large cylinderdisplacements. In an automotive application at low loads the secondarysystem is inoperative and the primary stage of the carburetor furnishesthe engine fuel air mixture requirements. As the load increases, thesecondary stage of the carburetor becomes operative to furnish, inconjunction with the primary stage, the additional mixture requirementsof the engine.

The interrelated operation of the primary and secondary stages isgenerally controlled by a complex linkage system. The linkage frequentlyincludes an interlock which prevents the secondary system fromfunctioning when the choke valve is closed during warm-up periods. Thecomplex linkage conventionally employed requires detailed adjustmentduring initial setup and when engine tune ups are being performed.

The point at which the secondary stage of the carburetor comes intooperation varies from carburetor to carburetor. Generally, however, thelinkage permits the secondary system to become operative at a pointconsiderably prior to wide open throttle of the primary system. Thelinkage then permits a secondary throttle valve to open at anaccelerated rate so that the primary and secondary systems may reachfull throttle condition simultaneously.

The construction in current production vehicles is such that thesecondary throttle valve is permitted to open even though theaccelerator pedal is only slightly depressed. The corresponding load atwhich the secondary stage becomes operative is frequently so low that,even under steady speed condition, all the throttle valves are at leastpartially opened under most conditions of operation. The entirecarburetors calibration, therefore, must be a compromise between lowspeed economy and maximum performance at full throttle resulting in asacrifice of economy at normal operating speeds.

The poor part throttle fuel economy and complicated linkage ofconventional four barrel carburetors has prevented extensive acceptanceof these carburetors. In addition, many manufacturers who previouslyutilized two stage carburetors are returning to single stage carburetorseither as original equipment or as a regular production option.

It is an object of this invention to provide a two stage carburetor thatpossesses good part throttle economy without sacrificing full throttleperformance.

It is a still further object of this invention to provide a secondarystage control mechanism that requires a minimum number of parts andadjustments.

The carburetor throttle Valve control mechanism of the present inventionprevents opening of the secondary throttle valve until the primarythrottle valve is at, or nearly at, full throttle. Continued movement ofthe primary throttle valve allows the secondary throttle valve to openat an accelerated rate. The construction permits 3,259,376 Patented July5, 1966 the primary throttle valve to reach its full throttle positionbefore the secondary throttle valve is fully opened. This permits theprimary system to be designed and calibrated for economy because maximumperformance requirements are met by the secondary system. Theconstruction further eliminates the requirements of a choke operatedthrottle valve lock in the secondary system inasmuch as the secondarythrottle valve cannot open until the primary throttle valve is at wideopen throttle.

As a further economy feature of the present invention, the secondarythrottle valve is actually opened in response to engine demand asexpressed by manifold vacuum. The degree of opening of the secondarythrottle valve is limited by the linkage of the present invention.

Further objects and advantages of this invention will become moreapparent as this description proceeds particularly when considered inconjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of a two stage carburetorincorporating the present invention.

FIGS. 25 show, in enlarged view, the linkage of the present invention inseveral stages of operation.

FIG. 6 is a cross sectional view taken along line 66 of FIG. 2.

FIG. 7 is a cross sectional view taken along line 7-7 of FIG. 2.

Referring now in detail to the drawings and in particular to FIG. 1,there is shown generally at 11 a two stage or four barrel carburetor.Carburetor 11 has the primary and secondary venturis 12 and 13respectively. The detail of the internal construction of carburetor 11is not shown since that construction is well known in the art and formsno part of the present invention. The primar ysystem will be designedand calibrated primarily for economy while the secondary system isdesigned to satisfy the maximum performance requirements of the engine.As is conventional, choke valve 14 is positioned in primary venturi 12.

Fuel and air flowing through primary venturi 12 is regulated by theprimary throttle valve 15 rotatably positioned therein on a shaft 16. Asecondary throttle valve 17 is rotatably positioned on a shaft 18 insecondary venturi 13 to control the flow of mixture therethrough.

The linkage controlling the operation of primary and secondary throttlevalves 15 and 17 is shown generally at 19 and in more detail in FIGS.27. Linkage 19 includes a first link 21 which is suitably and rigidlysecured to primary throttle valve shaft 16 for rotation therewith. Amanually actuated cam link 22 rotatably supported on primary throttlevalve shaft 16. It will be readily apparent that cam link 22 is actuatedby the vehicular accelerator pedal in the known manner. The hole 23 isprovided in cam link 22 to allow attachment of the accelerator linkage.A torsional mouse trap type spring .24 coacts with links 21 and 22 tourge the inturned tang 25 formed on link 21 into contact with cam link22 (FIGS. 2 and 3). The action of spring 24 causes links 21 and 22 torotate together as a unit until the primary throttle valve 15 reachesthe wide open throttle position (FIG. 4). Primary throttle valve 15 maythereby be manually positioned by movement of the vehicular acceleratorpedal.

The opening of the secondary throttle valve 17 is controlled by thefollower link 26. If mechanical actuation of secondary throttle valve 17is desired, follower link 26 may be directly secured for rotation withsecondary throttle valve shaft 18. To provide increased economy,however, vacuum actuation of secondary throttle valve is desired. Thisinsures that secondary throttle valve 17 will not open until enginedemand so requires. For this purpose, secondary throttle valve 17 may beopened by any of the vacuum or air flow responsive devices known in theart. It has been found most desirable to utilize an overcenter balancevalve of the type well known in the art. A link 27 is rigidly securedfor rotation with secondary throttle shaft 17 to limit the maximumopening permitted secondary throttle valve 17. A leaf spring 28 securedto the inturned tang 29 formed on link 27 contacts follower link 26(FIG. 7). The position of follower link 26, therefore, positively limitsthe maximum opening of secondary throttle valve 17 and the flow of fuelair mixture through secondary venturi 13.

OPERATION Cam link 22 and follower link 26 are constructed to providethree stages of operation for carburetor 11. During the initial stage ofoperation, movement of manually controlled cam link 22 is directlytransmitted to movement of primary throttle valve 15 through torsionalspring 24. In this stage of operation, the arcuate or first cam portion31 formed on link 22 urges follower link 26 in a direction whichprevents secondary throttle valve 17 from opening through contact with apart of the follower portion formed on follower link 26, that is theinturned tang 32 formed thereon (FIG. 2).

In the second stage of operation, cam portion 31 moves free of contactwith tang 32 and a pin or second cam portion 33 secured to cam link 22enters the slot 34 formed in follower link 26 (FIG. 3). This occurs whenprimary throttle valve 15 is at or nearly at its full throttle position.A point five degrees before wide open throttle of the primary system hasproven desirable. Continued movement of cam link 22 and primary throttlevalve 15 is accompanied by movement of the follower link 26 at anaccelerated rate because of the action of pin 33 with another part ofthe follower portion on the follower link 26, that is one wall formingthe edge of slot 34. This is the bottom edge of the slot 34 as viewed inFIGURES 3 and 4. This permits secondary throttle valve 17 to be openedin response to engine demand as expressed by manifold vacuum.

When primary throttle valve 15 is fully opened, it is prevented fromfurther movement by the contact of the adjustable stop 35 threadedthrough an aperture formed in tang 25 with an abutment 36 formed on thecarburetor body (FIG. 4). This occurs prior to the wide open throttleposition of secondary valve 17. Continued movement of cam link 22 ispermitted by the yielding of torsional spring 24. This permits followerlink 26 to be positioned so that secondary throttle valve 17 may move inresponse to the proper engine vacuum to the wide open position. Theactual position will, of course, be dependent upon the engine vacuum.FIGURE illustrates the linkage and throttle valves in the fully openthrottle position.

It is to be understood that this invention is not to be limited tothe-construction shown and described but that various changes andmodifications may be made within the scope of the invention as definedby the appended claims:

What is claimed is:

1. A multistage carburetor having primary and secondary mixtureconduits, a primary throttle valve located upon a primary throttle valveshaft in said primary mixture conduit, a secondary throttle valvelocated upon a secondary throttle valve shaft in said secondary mixtureconduit, a cam link supported on said primary throttle valve shaft forcontrolling the position of said primary throttle valve, and followerlink supported on said secondary throttle valve shaft for controllingthe position of said secondary throttle valve, a first cam portionformed on said cam link, a follower portion formed on said followerlink, said first cam portion and said follower portion being formed tocoact for precluding the opening of said secondary throttle controlvalve during a first portion of the movement of said primary throttlevalve and said cam link, and a second cam portion formed on said camlink for coacting with the follower portion on said follower link forcausing movement of said follower link to permit opening of saidsecondary throttle valve during a second portion of the movement of saidcam link.

2. A multistage fuel induction device having primary and secondarymixture conduits, a primary throttle valve located upon a primarythrottle valve shaft in said primary mixture conduit, a secondarythrottle valve located on a secondary throttle valve shaft in saidsecondary mixture conduit, a first link fixed to said primary throttlevalve shaft for controlling the position of said primary throttle valve,a cam link rotatably supported upon said primary throttle valve shaft, afollower link supported on said secondary throttle valve shaft forcontrolling the position of said secondary throttle valve, biasing meansinterposed between said first link and said cam link for simultaneousmovement of said first link and said cam link, means for positioningsaid cam link, a first cam portion formed on said cam link, a followerportion formed on said follower link, said cam portion and said followerportion being formed to coact for precluding the movement of saidfollower link and opening of said secondary throttle valve during afirst range of movement of said cam link, and a second cam portionformed on said cam link for cooperation with the follower portion ofsaid follower link to cause movement of said follower link and permitopening of said secondary throttle valve during a second range ofmovement of said cam link.

References Cited by the Examiner UNITED STATES PATENTS 2,640,472 6/ 1953Bicknell. 2,749,100 6/ 6 Carlson. 2,914,052 11/1959 Read.

HARRY B. THORNTON, Primary Examiner.

R. R. WEAVER, Assistant Examiner.

1. A MULTISTAGE CARBURETOR HAVING PRIMARY AND SECONDARY MIXTURECONDUITS, A PRIMARY THROTTLE VALVE LOCATED UPON A PRIMARY THROTTLE VALVESHAFT IN SAID PRIMARY MIXTURE CONDUITT, A SECOND THROTTLE VALVE LOCATEDUPON A SECONDARY THROTTLE VALVE SHAFT IN SAID SECONDARY MIXTURE CONDUIT,A CAM LINK SUPPORTED ON SAID PRIMARY THROTTLE VALVE SHAFT FORCONTROLLING THE POSITION OF SAID PRIMARY THROTTLE VALVE, AND FOLLOWERLINK SUPPORTED ON SAID SECONDARY THROTTLE VALVE SHAFT FOR CONTROLLINGTHE POSITION OF SAID SECONDARY THROTTLE VALVE, A FIRST CAM PORTIONFORMED ON SAID CAM LINK, A FOLLOWER PORTION FORMED ON SAID FOLLOWERLINK, SAID FIRST CAM PORTION AND SAID FOLLOWER PORTION BEING FORMED TOCOACT FOR PRECLUDING THE OPENING OF SAID SECONDARY THROTTLE CONTROLVALVE DURING A FIRST PORTION OF THE MOVEMENT OF SAID PRIMARY THROTTLEVALVE AND SAID CAM LINK, AND A SECOND CAM PORTION FORMED ON SAID CAMLINK FOR COACTING WITH THE FOLLOWER PORTION ON SAID FOLLOWER LINK FORCAUSING MOVEMENT OF SAID FOLLOWER LINK TO PERMIT OPENING OF SAIDSECONDARY THROTTLE VALVE DURING A SECOND PORTION OF THE MOVEMENT OF SAIDCAM LINK.